Apparatus for transferring between two heat conducting surfaces

ABSTRACT

An apparatus for transferring heat between two surfaces is provided. The apparatus includes a first support plate, a sheet of thermal material adjacent the first support plate, and a second support plate adjacent the sheet of thermal material, wherein the sheet of thermal material is disposed between the first support plate and the second support plate. The apparatus also includes at least one bolt inserted through each of the first support member, the sheet of thermal material, and the second support plate, the at least one bolt configured to be secured into a chassis. Finally, at least one spring is disposed between a shoulder of the at least one bolt and the second support plate.

BACKGROUND

For many devices removing heat is essential in order to keep the device operating effectively. To aid in removal of heat from the device, generally a heat sink is coupled to the device. The heat sink is generally sized according to the amount of heat that the device will be dissipating. In many cases, however, space around the device generating heat is limited. Generally, however, there are other heat sinks or possible heat dissipating materials near the heat sink. Each of these additional heat sinks may not be coupled to a device generating the same amount of heat, and may have extra cooling capacity.

The heat dissipation problems are increased when using heat sinks with electronic devices, because many electronic devices generate a large amount of heat in a relatively small area. For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an apparatus and method for improving the heat dissipation of devices within a chassis.

SUMMARY

An apparatus for transferring heat between two surfaces is provided. The apparatus includes a first support plate, a sheet of thermal material adjacent the first support plate, and a second support plate adjacent the sheet of thermal material, wherein the sheet of thermal material is disposed between the first support plate and the second support plate. The apparatus also includes at least one bolt inserted through each of the first support member, the sheet of thermal material, and the second support plate, the at least one bolt configured to be secured into a chassis. Finally, at least one spring is disposed between a shoulder of the at least one bolt and the second support plate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more easily understood, and further advantages and uses thereof are more readily apparent, when considered in view of the detailed description and the following figures in which:

FIG. 1 is an exploded view of one embodiment of a heat transfer device for transferring heat between two surfaces;

FIG. 2A is a side view of the heat transfer device of FIG. 1;

FIG. 2B is a side view of the heat transfer device of FIG. 1;

FIG. 2C is a side view of the heat transfer device of FIG. 1;

FIG. 2D is a perspective view of the heat transfer device of FIG. 1; and

FIG. 3 is a perspective view of the heat transfer device of FIG. 1 in a chassis.

In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific illustrative embodiments in which the method and system may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.

Embodiments of the present invention provide for an apparatus for transferring heat between two surfaces. The apparatus includes a sheet of thermal material contacts one heat conducting surface on one side and a second heat conducting surface on the other side. The sheet of thermal material is part of an assembly and is placed between two sheets of metal to support the thermal material. The assembly of the sheet of metal and the thermal material are mounted via a fastener to a desired structure and a spring is inserted between the fastener and the assembly. The assembly can pivot relative to the fastener and the mounting structure to allow the thermal material to make solid contact with each heat conducting surface, yet still allow one or both heat conducting surfaces to be moved out of contact with the thermal material when not transferring heat.

FIG. 1 is an exploded view of one embodiment of a heat transfer device 100 for transferring heat between two heat dissipation members. Heat transfer device 100 includes a back support plate 102, a sheet of thermal material 104, a front support plate 106, two fasteners 108, and two springs 110. Heat transfer device 100 uses thermal material 104 to facilitate transfer of thermal energy (heat) from one surface to a nearby surface.

Thermal material 104 acts as the heat transfer medium for heat transfer device 100. Heat transfer occurs through contact between thermal material 104 and each heat conducting member. One heat conducting member (shown in FIG. 3) contacts thermal material 104 on first side 112 and the other heat conducting member (also shown in FIG. 3) contacts thermal material 104 on a second side 114. In one embodiment, the two heat conducting members are oriented at a right angle with respect to one another. Thus, heat transfer device 100 is oriented at approximately a 45 degree angle with respect to each heat conducting member. To assure good contact with each heat conducting member, each side 112, 114 of heat transfer device is beveled. Thus each side 112, 114 can make flat contact with each heat conducting member.

Thermal material 104 is a material having a high thermal conductivity in the direction of desired propagation of heat. In this embodiment, the heat is transferred from side 112 to side 114, thus thermal material 104 has a high thermal conductivity in the a-direction. The higher the thermal conductivity of thermal material 104, the better propagation of heat between the two heat conducting members. Most materials having the high thermal conductivity desired for this application, however, do not possess the strength to withstand pressing at an angle against another surface.

In one embodiment, thermal material 104 is a material having a high thermal conductivity in the a-b plane. For example, in one embodiment, thermal material 104 is thermal pyrolytic graphite (TPG). TPG is commercially available from Momentive Performance Materials in Wilton, Conn. TPG may be referred to as highly oriented pyrolytic graphite (HOPG), or compression annealed pyrolytic graphite (CAPG), and refers to graphite materials consisting of crystallites of considerable size, the crystallites being highly aligned or oriented with respect to each other and having well ordered carbon layers or a high degree of preferred crystallite orientation, with an in-plane thermal conductivity greater than 1000 W/m-K. In one embodiment, TPG has an in-plane thermal conductivity of approximately 1,500 W/m-K. Here, TPG is oriented such that the in-plane of the TPG is aligned with the a-b plane in FIG. 1. Thus, the TPG efficiently propagates heat between the first side 112 of thermal material 104 and the second side 114. In an alternative embodiment, thermal material 104 is a diamond-like-carbon (DLC) or other diamond material having a high in-plane thermal conductivity.

For extra support, thermal material 104 is placed between back support 102 and front support 106. Each of back support 102 and front support 106 is composed of a rigid material capable of withstanding pressure placed by fasteners 108 with minimal bending. The minimal bending helps prevent the brittle thermal material 104 from cracking. In one embodiment, back plate 102 and front plate 106 are aluminum. In an alternative embodiment, back plate 102 is copper and front plate 106 is steel. Both back plate 102 and front plate 106 are generally flat sheets having two apertures 116 for accepting fasteners 108. As shown in FIG. 1, front sheet 106 has a curved top and bottom flange for additional strength in maintaining the shape of front plate 106.

In one embodiment, TPG is formed as described in U.S. Pat. No. 5,863,467 which is hereby incorporated herein by reference. Briefly, to manufacture heat transfer device 100 with TPG, pyrolytic graphite is deposited between back support member 102 and front support member 106. Heat transfer device 100 is then heat treated to form the pyrolytic graphite into a crystal structure. The resulting crystal structure, TPG, has a high in plane conductivity.

Each fastener 108 attaches thermal transfer device 100 to a structure. In this embodiment, each fastener 108 is a bolt which is placed through an aperture 116 of each of front support 102, thermal material 104, and back support 106. In one embodiment, fastener 108 has a shoulder for spring 110 to seat upon. In this embodiment, spring 110 is a helical coil spring placed around fastener 108 and between the shoulder of fastener 108 and front plate 106. In an alternative embodiment, spring 110 contacts shoulder of fastener 108, is only along the side of fastener 108 and not around fastener 108. In other embodiments, spring 110 is mounted between fastener 108 and front plate 106 in other manners as known to those skilled in the art. Additionally, in other embodiments, spring 110 is a metal leaf spring or a compliant rubber bushing. Further, although as shown in FIG. 1, fasteners 108 are bolts, other fasteners could be used. For example, in an alternative embodiment, fasteners 108 are screws or rivots. In another embodiment, fasteners 108 attach directly to back plate 102 on one end and to the structure which heat transfer device 100 is mounted to on another end. Thus, back plate 102, thermal material 104, and/or front plate 106 do not have apertures for fasteners.

Referring now to FIGS. 2A, 2B, 2C, and 2D, side and perspective views of heat transfer device 100 are shown. FIG. 2A illustrates a view of heat transfer device 100 where back plate 102 is forward. As can be seen, along with the beveled edges of thermal material 104, both back plate 102 also has beveled edges. Additionally, back plate 102 has a slightly smaller width than the sheet of thermal material 104. The slightly smaller width of back plate 102 aligns beveled edges to enable heat transfer device 100 to contact both the first and the second heat conducting members.

FIG. 2B illustrates a side view of heat transfer device 100 showing springs 110 seated against both front plate 106 and fasteners 108. As shown each spring 110 is in a position of rest. Springs 110 ensure solid contact between heat transfer device 100 and each heat conducting member while allowing flexibility in the positioning of heat transfer device 100 and each heat conducting member. When heat transfer device 100 is pressed against each heat conducting member (or each heat conducting member is pressed against heat transfer device), the assembly of back plate 102, thermal material 104, and front plate 106, the assembly compresses springs 110 against fasteners 108. Fasteners 108 and therefore heat transfer device 100 are set such that springs 110 are partially compressed when heat transfer device 100 is in a resting contact position with each heat conducting member. Thus, springs 110 maintain a constant pressure for heat transfer device 100 against each heat conducting member.

Referring now to FIG. 3, one embodiment of heat transfer device 100 in a chassis 300. In this embodiment, chassis 300 holds electronics which dissipate heat to the outside of chassis 300 with a plurality of heat sinks 302, 304. Each of heat sinks 302, 304 is located on a door which pivots open to allow access to the inside of chassis 300. Heat sink 302 has an electronics module 306 mounted thereupon. To increase the heat dissipation from electronics module 306, heat transfer device 100 transfers heat from (warmer) heat sink 302 to (cooler) heat sink 304.

Heat transfer device 100 is mounted in a corner between heat sink 302 and heat sink 304. Fasteners 108 of heat transfer device 100 are secured into a portion of chassis 300. When doors are opened heat transfer device 100 is not in contact with heat sinks 302, 304, and heat transfer device 100 remains secured to chassis 300 with springs 110 in a resting position. When each door of heat sink 302 and 304 is closed, a heat conductive surface of each heat sink 302, 304 comes into contact with the beveled edge of thermal material 104. As each heat sink 302, 304 contacts heat transfer device 100, heat transfer device is allowed to translate along each fastener 108 and pivot slightly. This allows heat transfer device 100 to adjust to each heat sink 302, 304 as they move and contact heat transfer device 100.

Advantageously, heat transfer device 100 enables heat transfer between two heat conducting members without permanent connection to the heat conducting members. One or both heat conducting members to be movable, while still allowing each heat conducting member to transfer heat when in contact with heat transfer device 100. As shown in FIG. 3, both fasteners 108 are aligned vertically with one another. This permits heat transfer device 100 to pivot horizontally about an axis intersecting each fastener 108. Additionally, each fastener 108 is located in the middle horizontally of front plate 106, thermal material 104, and back plate 102, thus enabling heat transfer device 100 to pivot equally in either direction. In an alternative embodiment, a single fastener is used, thus allowing easier pivoting of heat transfer device 100 in the vertical and horizontal directions. In other embodiments, fasteners 108 are located in different locations to produce different pivot axis, or no pivot axis at all.

Although FIG. 3 heat transfer device 100 is illustrated as transferring heat between two surfaces which are angled at 90 degrees with respect to one another, other angles of surfaces could also be used that are less than 180 degrees. For example, in one embodiment, heat sink 302 and heat sink 304 are at a 45 degree angle away from each other. Here, the angle of the bevel on thermal material 104 would be match the angle of each heat conducting surface.

In an alternative embodiment, multiple heat transfer devices are used to transfer heat between two surfaces. Multiple heat transfer devices are used, for example, to conform to a non-flat surface. When the surface or surfaces from which heat is transferred between have variations, a different heat transfer device can be used to match the different angled section of the surface. Additionally, the length and width of the heat transfer device, or devices can be changed to conform to the surfaces, the amount of heat transfer, or surrounding devices. Finally, in one embodiment, a strip of conductive pad material is used along each edge of heat transfer device 100 to improve contact with a heat conducting member.

Further, although FIG. 3 illustrates heat transfer device 100 as transferring heat between two heat sinks 302, 304, other heat conducting members could be used. For example, in one embodiment, heat transfer device 100 transfers heat between a heat sink and a chassis. In other embodiments, heat transfer device 100 transfer heat between a heat sink and a cooling liquid. Finally, in an alternative embodiment, springs 110 are located on the back plate 102 of heat transfer device. The precise location of springs 110 is not critical, as long as springs 110 provide coupling between fasteners 108 and thermal material 104, and force for thermal material 104 against a heat conducting member.

Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to base any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof. 

1. An apparatus for transferring heat between two surfaces, the apparatus comprising: a first support plate; a sheet of thermal material adjacent the first support plate; a second support plate adjacent the sheet of thermal material, wherein the sheet of thermal material is disposed between the first support plate and the second support plate; at least one bolt inserted through each of the first support member, the sheet of thermal material, and the second support plate, the at least one bolt configured to be secured into a chassis; and at least one spring disposed between a shoulder of the at least one bolt and the second support plate.
 2. The apparatus of claim 1, wherein the sheet of thermal material is composed of thermal pyrolytic graphite.
 3. The apparatus of claim 1, wherein the first support plate and the second support plate are aluminum.
 4. The apparatus of claim 1, wherein at least one side of the sheet of thermal material is beveled.
 5. The apparatus of claim 1, wherein the spring is a helical spring.
 6. The apparatus of claim 1, wherein the sheet of thermal material is configured to transfer heat between two surfaces which are at an angle of 90 degrees relative to each other.
 7. The apparatus of claim 1, wherein the back support, the sheet of thermal material, and the front support are configured to translate along the at least one bolt and against the at least one spring.
 8. The apparatus of claim 1, wherein the at least one spring is configured to apply pressure for the sheet of thermal material against at least one heat conducting surface.
 9. The apparatus of claim 1, wherein the sheet of thermal material is configured to transfer heat from a first side to a second side of the sheet.
 10. The apparatus of claim 1, wherein the at least one bolt comprises a first bolt and a second bolt, and wherein an axis intersecting the first bolt and the second bolt is aligned with at least one side of the sheet of thermal material that is configured to contact a heat conducting surface.
 11. An apparatus for transferring heat between two surface, the apparatus comprising: a thermal material having a first thermal conductivity in one plane and a second thermal conductivity in a direction normal to the plane, the first thermal conductivity being greater than a the second thermal conductivity; at least one fastener configured to fasten the thermal material to a structure, the at least one fastener configured to allow translational movement of the thermal material; and at least one spring disposed between the at least one fastener and the thermal material, the at least one spring configured to apply pressure for the sheet of thermal material against at least one heat conducting surface when contact between the at least one heat conducting surface and the thermal material occurs.
 12. The apparatus of claim 11, wherein the thermal material is formed into a sheet.
 13. The apparatus of claim 11, wherein thermal material is composed of thermal pyrolytic graphite.
 14. The apparatus of claim 11, further comprising a first support plate and a second support plate, wherein the thermal material is disposed between the first support plate and the second support plate.
 15. The apparatus of claim 11, wherein at least one side of the thermal material is beveled.
 16. The apparatus of claim 1, wherein the spring is a helical spring.
 17. The apparatus of claim 11, wherein the thermal material is configured to transfer heat between two surfaces which are at an angle of 90 degrees relative to each other.
 18. The apparatus of claim 11, wherein the sheet of thermal material is configured to transfer heat from a first side to a second side of the sheet.
 19. The apparatus of claim 11, wherein the at least one fastener comprises a first bolt and a second bolt, and wherein an axis intersecting the first bolt and the second bolt is aligned with at least one side of the thermal material that is configured to contact a heat conducting surface.
 20. An apparatus for transferring heat between two surfaces, the apparatus comprising: a first support sheet having at least one aperture; a sheet of thermal material having at least one aperture, the sheet of thermal material adjacent the first sheet of metal wherein the at least one aperture of the first sheet of metal and the sheet of thermal material are aligned, the sheet of thermal material having a first thermal conductivity in a plane parallel to the sheet of metal and a second thermal conductivity in a direction normal to the plane, the first thermal conductivity being greater than a the second thermal conductivity; a second support sheet having at least one aperture, the second support sheet adjacent the sheet of thermal material, wherein the sheet of thermal material is disposed between the first support plate and the second support plate and the at least one aperture in the second support sheet is aligned with the at least one apertures of the first support sheet and the sheet of thermal material; at least one bolt, each of the at least one bolts inserted through one of the least one apertures of the second support sheet, the sheet of thermal material, and the first support sheet; and at least one spring disposed between a shoulder of the at least one bolt and the second support plate.
 21. The apparatus of claim 20, wherein the thermal material is thermal pyrolytic graphite.
 22. The apparatus of claim 20, wherein the first support sheet and the second support sheet are composed of metal. 